The invention relates to a selective process for hydrosilylation of dihydridosiloxanes in the manufacture of asymmetric organosiloxanes containing at least one polyalkylene oxide group. More specifically, the invention relates to a method to make an asymmetric siloxane containing at least one polyalkylene oxide group and novel compositions.
Organosiloxanes containing polyalkylene oxide groups may be used as dispersants, wetting agents, spreading agents and emulsifiers in agricultural chemical formulations and in other wetting, spreading, foaming and detergent applications. Formulations containing organosiloxanes are commonly used in forestry, agriculture, and horticulture as agricultural adjuvants to improve efficacy of agrochemical active ingredients such as micronutrients, growth regulators, biologicals, pesticides such as herbicides, fungicides, insecticides, acaracides and miticides.
Organosiloxanes may be formed from a reaction of a hydridosiloxane with an olefin such as an aliphatic olefin or olefin-terminated polyalkylene oxide such, as ally-, vinyl- and methallyl-terminated polyalkylene oxides. Likewise, olefins such as allyl chloride or 1-octene may be reacted with a hydridosilane such, as trimethoxysilane in the presence of an appropriate precious metal catalyst. These precious metal catalysts include complexes of rhodium, ruthenium, palladium, osmium, iridium or platinum.
Many of these known organosiloxanes may only be used in aqueous formulations within a narrow pH range, ranging from a slightly acidic pH of 6 to a very mildly basic pH of 7.5. Outside this narrow pH range, these known organosiloxanes may not be stable to hydrolysis undergoing rapid decomposition. Recently, asymmetric organosiloxanes that contain, at least one polyalkylene oxide group have been disclosed that provide stable performance in aqueous formulations that are outside of this narrow pH range. However, these asymmetric organosiloxanes are difficult to manufacture because the processes are not selective. These processes generate mixtures of components that have undesirable characteristics, such as a decrease in the wetting and spreading properties of the organosiloxanes. Therefore, a need exists for an efficient, selective and cost effective process to make these asymmetric organosiloxanes.